You can use sum per page function to display sum of any columns values of that page and sum total function to display grand total. Please note that these function display values dynamically on crud table only.
$pdocrud = new PDOCrud();
$pdocrud->crudTableCol(array("product_id","product_name","product_price","product_sell_price"));
$pdocrud->colSumPerPage("product_price");
$pdocrud->colSumPerPage("product_sell_price");
$pdocrud->colSumTotal("product_sell_price");
echo $pdocrud->dbTable("products")->render();